An internal combustion engine may be combined with an electric machine to provide torque to propel a vehicle. The internal combustion engine provides rotational torque to the vehicle driveline as well as vacuum for operating various actuators and heat for the vehicle's passenger cabin. The electric machine may provide torque to propel the vehicle and it may also be operated as a generator to charge a vehicle battery. However, if the electric machine is propelling the vehicle when the engine is stopped and ambient temperature is low, an electrical heater may have to be used to heat the passenger cabin. Operating the electric heater may reduce the amount of time the engine may be deactivated since the electric heater consumes battery charge. Thus, vehicle fuel conservation may be reduced by operating the passenger cabin heater.
The inventors herein have recognized the above-mentioned disadvantages and have developed an engine system, comprising: an engine including an exhaust gas heat exchanger positioned along an exhaust system; a thermal energy storage device in fluidic communication with the exhaust gas heat exchanger; and an engine coolant heat exchanger in thermal communication with the thermal energy storage device.
By extracting engine exhaust gas heat to a thermal energy storage device, it may be possible to provide the technical result of propelling a vehicle and maintaining a passenger cabin temperature while an engine has stopped rotating. In particular, the thermal energy storage device may store exhaust gas energy while the engine is combusting an air-fuel mixture, and thermal energy may be released from the thermal energy storage device while the engine has stopped rotating while an electric machine is propelling the vehicle. In this way, it may be possible to provide heat to the vehicle cabin without consuming electrical energy in an electrical heater. In some examples, an engine coolant pump may be activated when heating the passenger cabin instead of operating an electric heater so that electrical power consumption may be reduced.
The present description may provide several advantages. In particular, the approach may extend an amount of time a hybrid vehicle may operate without activating an engine. Additionally, the approach may improve engine starting emissions and fuel economy by reducing engine warm-up time. Further, the approach may be realized with a limited amount of hardware.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.